Download Vitamins

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Vitamins
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Organic compounds
Vital to life
Indispensable to body functions
Needed in minute amounts
Noncaloric essential nutrients
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Two classes of vitamins:
Fat-soluble: A,D, E, K
◦ In general, absorbed into the lymph
◦ Travel in blood in association with protein carriers
◦ Stored in the liver or with other lipids in fatty tissues;
some can build up to toxic concentrations
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Water-soluble: B vitamins, vitamin C
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Absorbed directly into blood stream
Travel freely in blood stream
Most are not stored to any great extent
Excess excreted in urine
Lower risk of toxicity than fat-soluble vitamins
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A, D, E, K
◦ Found in fats and oils of foods
◦ Require bile for absorption
◦ Stored in liver and fatty tissues until the body needs
them
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Body can survive weeks of consuming foods
that lack these vitamins
◦ As long as a diet as a whole provides average
amounts that approximate recommended intakes
◦ Excess vitamins A and D from supplements can
easily reach toxic levels
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Deficiency is likely when diet is consistently
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Fat malabsorption diseases can cause loss in
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Extraordinarily-low-fat diets
low in fat-soluble vitamins
dissolved undigested fat
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Functions:
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Vision
Maintenance of body linings and skin
Immune defenses
Growth of bones and the body
Normal cell development
Reproduction
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Excessive beta-carotene will not cause
vitamin A toxicity
◦ However, it can cause people to turn a bright yellow
due to deposition in subcutaneous fat
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Roles of vitamin D
◦ Regulation of blood calcium and phosphorus levels
 Often at a genetic level
 When more calcium is needed vitamin D acts to raise
blood calcium levels
 Draws calcium from bone
 Promotes calcium absorption
 Promotes calcium retention by the kidneys
◦ Functions as a hormone
◦ Plays a role in the brain, heart, stomach, pancreas,
skin, reproductive organs, some cancer cells,
stimulates cell maturation
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Deficiency promotes:
◦ High blood pressure, some cancers, type 1
diabetes, heart disease, rheumatoid arthritis,
multiple sclerosis
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Too Little Vitamin D - A Danger to Bones
◦ Rickets
 Vitamin D deficiency disease in children
 Characterized by abnormal bone growth
 Bowed, or knock-knees, outward-bowed chest, knobs
on ribs
© 2006 Thomson-Wadsworth
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Older individuals may have painful joints and
muscles due to low vitamin D levels
Osteomalacia, the adult form of rickets
◦ Characterized by an overabundance of
unmineralized bone protein
◦ Most often occurs in women with low calcium
intake and little exposure to the sun and who go
through repeated pregnancies and periods of
lactation
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Too Much Vitamin D - A Danger to Soft
Tissue
◦ Most potentially toxic of all vitamins
◦ Toxicity symptoms include: appetite loss, nausea,
vomiting, increased urination, increased thirst,
severe form of psychological depression due to
effects on the central nervous system
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If overdoses continue: dangerously high
blood calcium level, forcing calcium to be
deposited in soft tissues
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Not essential in the sense
that the body can make
all it needs with the help
of sunlight
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How Can People Make a Vitamin from
Sunlight?
◦ Most people rely on exposure to sunlight to
maintain adequate vitamin D nutrition
◦ UV exposure to a cholesterol compound in the skin
transforms it into a vitamin D precursor which is
absorbed into the blood
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Skin synthesis of vitamin D poses no risk of
toxicity
◦ The sun itself begins breaking down excess vitamin
D made in the skin
◦ Sunbathers are at risk of skin damage and skin
cancer
 Sunscreens with SPFs of 8 or above can reduce these
risks, but they also prevent vitamin D synthesis
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In most places, during warmer months, just
being outdoors when the sun is overhead,
even in lightweight clothing, promotes
sufficient skin synthesis of vitamin D
Factors affecting sun exposure and vitamin D
synthesis:
◦ Skin color, air pollution, city living, clothing,
geography, indoor lifestyle, season, sunscreen, time
of day
◦ African and Mexican Americans, may border on
vitamin D insufficiency
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Sources:
◦ Small amounts from butter, cream, fortified
margarine
◦ Fortified milk, sunlight
◦ Only two fortified plant sources exist: margarines
and certain cereals
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Consists of four tocopherol compounds
◦ Alpha, beta, gamma, delta
◦ Alpha-tocopherol is the standard for vitamin E
activity
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The Extraordinary Bodyguard
◦ Antioxidant
◦ Damage that results when free radicals formed
during normal metabolism disrupt the structure of
cellular lipids, DNA, proteins
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Free radical activity may lead to cancer, heart
disease, or other diseases
Vitamin E is preferentially oxidized, thus
protecting cells
Supplements do not provide health benefits
However, supplements may improve the
immune response in healthy elderly people
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Vitamin E Deficiency
◦ Wide variety of symptoms in laboratory animals,
most symptoms not reproduced in humans
◦ Vitamin E is widespread in food, making it difficult
to create a vitamin E-deficient diet
◦ Body stores large amounts in fatty tissues
◦ Cells recycle vitamin E
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Infants born before the transfer of vitamin E
from the mother to the infant
◦ Potential anemia
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Adults: loss of muscle coordination and
reflexes with impaired movement, vision, and
speech
Associated with fat malabsorption diseases
◦ disease or injury to the liver, gallbladder, pancreas
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Low intakes likely when extremely-low-fat
diets are consumed for years
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Vitamin E is destroyed by food processing
and heating
Chronically low intake may play a role in
other diseases
◦ Low body stores of vitamin E and selenium promote
viral virulence
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No toxicity from food sources
Ordinary supplemental doses over a period of
months do not seem to induce toxicity
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In humans, occasional reports of breast
soreness in women, nausea, intestinal
distress, fatigue, emotional distress , and
other vague complaints
Large doses may increase the effects of
anticoagulant medications
Brain hemorrhages may occur in smokers
taking 50 milligrams/day for over 6 years
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Widespread in foods
◦ Most raw oils
◦ 20% of dietary vitamin E comes from vegetable oils
◦ 20% from fruits and vegetables
 None of which qualify as a good source
◦ 15% from fortified cereals and other grain products
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Smaller amounts from meat, poultry, fish,
eggs, milk products, nuts, seeds
Wheat germ is a good source
Animal fats have almost no vitamin E
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Functions:
◦ Synthesis of blood clotting proteins
 Does not improve clotting in those with diseases such
as hemophilia
 Interferes with function of blood thinners
◦ Synthesis of normal form of bone proteins that bind
minerals to bone
 Adequate intake may reduce risk of hip fracture
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At birth newborns are given a dose of vitamin
K to hold them until vitamin K-producing
bacteria establish themselves in their
intestinal tract
© 2006 Thomson-Wadsworth
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Sources:
◦ Leafy green vegetables
 Cooked spinach and collard greens average 300
micrograms/3 ounces
 Lettuce, broccoli, other members of the cabbage family
average 100 micrograms/3 ounces
◦ Intestinal bacteria, canola and soybean oils,
fortified cereals
◦ 1 egg and 1 cup of milk: 25 micrograms each
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Deficiency
◦ Unlikely in adults
 Even if they seldom eat vitamin K-rich foods
◦ At risk:
 Newborns
 Those who have taken antibiotics that kill the
beneficial, along with the harmful, bacteria in their
intestinal tract
 Low bile production
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Vitamin C and the B Vitamins
◦ Cooking and washing with water leaches them out
of food
◦ Easily absorbed
◦ Excess easily excreted in urine
◦ Some can remain in lean tissues for 1+ months
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Toxicity
◦ Never from food
◦ Can occur from the large doses concentrated in
some vitamin supplements
 Though the usual result will be to have expensive urine
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The Work of Vitamin C
◦ Maintenance of connective tissues
 Formation and maintenance of collagen
 Component of bones, teeth, skin, tendons, scar tissue,
capillaries
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Scurvy
◦ Vitamin C (ascorbic acid) deficiency
◦ Hazard of long distance seagoing journeys of 200+
years ago
◦ To avoid scurvy, British sailors were given lime juice
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Deficiency Symptoms
◦ Most scurvy symptoms are due to the breakdown of
collagen
 Loss of appetite, growth cessation, loose teeth,
swollen ankles and wrists, tiny red spots in the skin
where blood has leaked out of capillaries, anemia
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Antioxidant
◦ Protects substances found in foods and the body by
being oxidized itself
◦ Some oxidized vitamin C is lost and must be
replaced by the diet
◦ In the intestines, protects iron from oxidation
 Thus promoting its absorption
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In the blood
◦ Protects blood from oxidation
◦ Protects and recycles Vitamin E
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Supplements seem useless against heart
disease, cancer, other diseases
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In test tubes, high concentrations of vitamin
C act as a prooxidant
◦ Activating oxidizing elements, such as iron and
copper
◦ One study of men given 500 milligrams/day
showed an increase in markers of oxidation
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Risk of scurvy in the U.S. is low, with the
exception of
◦ Some elderly people
 Low intakes of fruits and vegetables combined with a
poor appetite lead to low vitamin C intakes
◦ People addicted to alcohol or other drugs
◦ Infants fed cow’s milk who do not receive vitamin C
in formula, fruit juice, or other sources
 Breast milk and infant formula supply enough vitamin
C
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Studies are yet to conclusively show that
vitamin C can prevent or reduce the severity
of colds
One group of researchers have found the
following:
◦ Daily dosages of vitamin C, taken regularly, do not
prevent colds
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The same group of researchers have also
found
◦ Some small benefit from vitamin C in high doses (1
gram) taken at the onset of a cold
◦ This may shorten the duration of colds by about
1.5 days and reduce the severity of symptoms by
about 40%
 The effect may be greater in children then adults
 In adults, doses near the UL (2 grams/day) may be
required to produce any effect
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Both active and passive smoking introduce
oxidants that deplete vitamin C
◦ Intake recommendations are set high
 Males: 110 milligrams
 Females: 105 milligrams
◦ Vitamin C cannot protect against the damage
caused by exposure to tobacco smoke
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Food Sources of Vitamin C
◦ 300 milligrams: 1 cup orange juice for breakfast, salad
for lunch, stalk of broccoli, a potato for dinner
◦ Vitamin C in fruits and vegetables are prone to
destruction by heat and oxygen
 Fresh, raw, and quickly cooked are best
 Store properly and consume promptly
© 2006 Thomson-Wadsworth
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Role
◦ Energy metabolism
◦ Nerve processes and tissue response
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Deficiency: beriberi “I can’t, I can’t”
◦ Loss of sensation in the hands and feet, muscular
weakness, advancing paralysis, abnormal heart action
◦ Wet beriberi
 Characterized by edema
◦ Dry beriberi
 No edema
 Acute
© 2006 Thomson-Wadsworth
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Deficiency: Wernicke-Korsakoff Syndrome
◦ Alcohol abuse with severe thiamin deficiency
◦ Alcohol displaces food in the diet, impairs thiamin
absorption, promotes thiamin excretion in the urine
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Symptoms:
◦ Apathy, irritability, mental confusion,
disorientation, loss of memory, jerky eye
movements, staggering gait
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Treatment: thiamin injection
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Sources
◦ Small amounts in many foods
◦ Pork products, leafy green vegetables, whole grain
cereals, legumes
◦ DRI:
 Men: 1.2 mg/day
 Women: 1.1 mg/day
 Higher if pregnant or lactating
© 2006 Thomson-Wadsworth
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Role
◦ Energy metabolism of all cells
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Deficiency
◦ Likely when thiamin is deficient
◦ May go undetected because thiamin deficiency
symptoms are more severe
◦ At risk:
 Children who lack milk products and meat
 Perhaps some U.S. elderly
◦ Treatment: A diet that remedies riboflavin
deficiencies also remedies a thiamin deficiency
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Sources
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Milk and milk products
Leafy green vegetables
Whole-grain breads
Fortified cereals
Some meats
© 2006 Thomson-Wadsworth
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Role
◦ Energy metabolism
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Deficiency
◦ Pellagra
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Diarrhea
Dermatitis
Dementia
Death
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At risk for pellagra:
◦ Poorly nourished people living in urban slums
 Particularly those with alcohol addiction
◦ Still common in parts of Africa and Asia
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Sources
◦ Tryptophan, which is abundant in almost all
proteins, can be converted to niacin
 Thus a person eating adequate protein will not be
deficient in niacin
◦ Niacin in the diet is stated in terms of niacin
equivalents (NE)
 Accounts for conversion of tryptophan to niacin
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Toxicity
◦ Large doses of a form of niacin may be a part of a
treatment to lower blood lipids associated with
cardiovascular disease
 Do not try this at home
◦ Large doses of niacin can injure the liver, cause peptic
ulcers, cause vision loss
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Certain forms of niacin supplements in amounts
2x-3x the DRI can cause niacin flush:
◦ Dilation of the capillaries of the skin with perceptible
tingling that, if intense, can be painful
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Role
◦ DNA synthesis
◦ Metabolism of several amino acids
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Deficiency
◦ Because immature red and white blood cells and
cells of the GI tract divide rapidly, they are most
vulnerable to a deficiency
◦ Anemia
 Related to anemia of vitamin B12 malabsorption
◦ Diminished immunity
◦ Abnormal digestive function
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Deficiency may result from
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Inadequate intake
Illnesses that impair folate absorption
Increased excretion
Medications that interact with folate, or otherwise
increase the body’s need
With deficiency, some evidence for increased
◦ Cardiovascular risk
◦ Colon cancer risk
◦ Cervical cancer risk
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Neural tube birth defects
◦ Range from slight problems in the spinal cord to
mental retardation
◦ Severely diminished brain size
◦ Death shortly after birth
◦ Arise in the first few days or weeks of pregnancy
 Most women eat too few fruits and vegetables to
supply even 50% of the folate needed to prevent such
birth defects
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All enriched grain products are fortified with
folic acid
◦ An especially absorbable synthetic form of folate
◦ Since fortification began, folate intakes have
increased and there has been an almost 25% drop
in the national incidence of neural tube defects
 It is expected that there will also be declines in some
other birth defects and miscarriages
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Toxicity
◦ UL for synthetic folate from supplements and
enriched foods is 1,000 micrograms/day for adults
◦ Folate can mask vitamin B12 deficiency
◦ Excess folate may be antagonistic to the actions of
some anticancer drugs
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Sources
◦ Leafy green vegetables
◦ Fresh, uncooked vegetables and fruits
 The heat of cooking and oxidation that occurs during
storage destroy much of the folate in foods
◦ Eggs contain folate
◦ Orange juice and legumes contain folate
 Contain factors that may interfere with folate
absorption
◦ Milk may enhance folate absorption
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Medications
◦ Of all the vitamins, folate is most likely to interact
with medications
◦ Ten major groups of drugs, including antacids and
aspirin and its relatives, oral contraceptives,
anticonvulsants, smoke interfere with the body’s
use of folate
 Occasional use of these drugs is okay
 Frequent users need to pay attention to their folate
intake
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Role
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Deficiency
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Sources
◦ Vitamin B12 is activated by folate
◦ Folate is activated by vitamin B12
◦ Maintenance of the sheaths that surround and protect
nerve fibers
◦ Damaged nerve sheaths
◦ Creeping paralysis
◦ General malfunctioning of nerves and muscles
◦ Foods of animal origin
◦ Not in foods from plants
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Deficiency results in failure of folate to make
red blood cells
◦ Therefore, a vitamin B12 deficiency causes an
anemia (pernicious anemia) identical to that of
folate
 Large, immature red blood cells
◦ Treatment: administration of folate
 However, this allows the deficiency of B12 to continue
undetected
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At risk
◦ The possibility that folic acid enrichment of grains is
masking vitamin B12 deficiencies
◦ Especially among vegetarians and the elderly
 Individuals who generally depend heavily on grains and
consume little or no meat or other animal products
◦ Malabsorption problems
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The uninformed, strict vegetarian (vegan) is
especially at risk
◦ May not show signs of deficiency right away because the
body stores up to six years’ worth of the vitamin
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Pregnant or lactating vegetarian women may
put their infant at risk of a vitamin B12
deficiency
◦ Resulting in irreversible nerve system damage
 Recognized when the infant displays nerve and
cognitive problems that can last into childhood
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All strict vegetarians must be sure to use
vitamin B12-fortified products
◦ Vitamin B12-fortified soy drink, supplements
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Absorption
◦ Requires intrinsic factor
 A compound made by the stomach
 The stomach’s acid liberates vitamin B12 from food; intrinsic
factor then binds to the vitamin
 The complex is then absorbed from the small intestine into
the blood
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In later years, many people lose the ability to
produce sufficient stomach acidity and intrinsic
factor
◦ Leaving them with reduced ability to absorb vitamin B12
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Treatment for defective absorption is B12
injections
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Role
◦ 100+ reactions in the tissues
◦ Needed to convert one kind of amino acid into
other nonessential amino acids
◦ Aids in the conversion of tryptophan to niacin
◦ Hemoglobin synthesis
◦ Neurotransmitter synthesis
 For example, assists in the conversion of tryptophan to
serotonin
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Role (continued)
◦ Assists in release of stored glucose from glycogen
 Contributing to the regulation of blood glucose
◦ Immune function
◦ Steroid hormonal activity
◦ Fetal brain and nervous system development
 Deficiency during this stage causes behavioral
problems later
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Deficiency
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Weakness
Psychological depression
Confusion
Irritability
Insomnia
Greasy dermatitis
Advanced cases of deficiency: convulsions
May weaken the immune system
Evidence that low intakes may be related to
increased risk of heart disease
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Sources
◦ Protein-rich foods
 Meats, fish, poultry
◦ Potatoes, leafy green vegetables, some fruits
◦ Legumes and peanut butter
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Toxicity
◦ Women who took 2+ grams/day for 2+ months in a
mistaken attempt to cure PMS symptoms
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Numb feet
Lost sensation in their hands
Eventually became unable to walk or work
Recovered after they stopped taking the supplements
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Role
◦ Energy metabolism
◦ Cofactor for several enzymes in the metabolism of
carbohydrate, fat, protein
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Deficiency
◦ Rare diseases
◦ Consumption of 24+ raw egg whites per day, which
contain a protein that binds biotin,will result in a
deficiency
 Cooking eggs denatures this protein
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Sources
◦ Wide spread in foods
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Role
◦ Energy metabolism
◦ Coenzyme that plays a role in the release of energy
from the energy nutrients
◦ Plays a role in 100+ steps concerned with the
synthesis of lipids, neurotransmitters, and
hemoglobin
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Deficiency
◦ Rare diseases
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Sources
◦ Widespread in foods